The present invention relates to a semiconductor device having an ultraviolet detecting section for detecting irradiation of ultraviolet rays.
At present, electrically erasable programmable read only memories (EEPROMs) are being used as general external memory devices in portable computers giving importance to communication functions. The EEPROM is advantageous in that data can be electrically written/erased in/from individual memory cells. However, data stored in the EEPROM is naturally erased by irradiation of ultraviolet rays.
For this reason, as disclosed in Japanese Utility Model Laid-Open No. 5-38915, a light-shielding film is conventionally formed on an EEPROM cell to shield ultraviolet rays which causes a data erase.
Since the light-shielding film is conventionally formed on the EEPROM cell, the semiconductor device operates even if the light-shielding film is damaged so that the EEPROM cell is irradiated with ultraviolet rays. In this case, no operation abnormality is detected though data of some cells are unintentionally erased. The semiconductor device having a defective EEPROM in which some of stored data become abnormal is undesirably used.
When such an EEPROM is used as an external memory device of a computer, the computer may run away owing to destroyed data.